Electro-acoustical loudspeakers are widely used and traditionally comprise a chassis in which a driver and a membrane are arranged. The driver is typically a magnetic system defining an air gap, in which air gap the magnets have been arranged such that a magnetic flux will be present across the gap. By having a voice coil connected to the membrane and arranging set voice coil in the air gap and furthermore connecting the coil to an amplifier, the current in the coil will be influenced by the magnetic field in the gap and thereby move up and down depending on the direction of the current in the coil.
The voice coil is traditionally connected to the membrane such that, as the voice coil moves back and forth in the air gap, the membrane will move accordingly and thereby create the sound.
From JP 2006041783 is a speaker system known comprising a membrane consisting of two dome shaped annulus arranged coaxially. The coil is attached to the connection between the inner and outer annulus and arranged in an air gap in the driver motor. The centre portion of the inner annulus is fastened to an upper portion of the loudspeaker driver motor. As the coil moves up and down in the airgap, sound will emit from the surface of the membrane. The emission direction will be substantially perpendicular to the surface of the membrane, in each point on the membrane. In action the inner annulus will thereby emit sound (waves) towards the center from the portions of the membrane being angled towards the central portion of the membrane. Theses sound waves will instantly interfere with sound waves deriving from the same membrane part diametrically opposite on the membrane. This interference will cause a certain degree of distortion in the resulting “sound picture”.